This invention relates to an improved melt-spinning process for preparing polyester yarns, the improvement involving the use of a stepped spinneret, whereby there may be prepared polyester yarns that may be draw-textured to produce fabrics having a spun-like feel similar to that of cotton or wool, and polyester yarns that may be air-jet textured to give bulked yarns of interesting properties.
Several suggestions have been made for preparing polyester yarns having a spun-like feel.
It is known to treat polyester yarn in a texturing jet to give it a more natural spun-like feel--see U.S. Pat. No. 4,100,725 to Magel. It is also known to produce filaments having body and wing portions. Filaments in such yarns when treated in a texturing jet tend to split longitudinally so that the wing portions are at least intermittently separated from the body portion. The wing portion also splits transversely giving a product with free ends--see U.S. Pat. No. 4,245,001 to Phillips et al. Mirhej Pat. No. 4,157,419 discloses a polyester draw-texturing feed yarn having three types of filaments, one of which is a bicomponent filament. When this yarn is hot drawn the bicomponent filaments break and the ends form a helical crimp.
Bradley et al U.S. Pat. No. 4,110,965 discloses a process for making a polyester yarn having a spun-like hand by breaking in a false twist operation one type of filaments (nonround filaments) while the second type of filaments (round filaments) remain unbroken. Bradley discloses first melt-spinning poly(ethylene terephthalate) homopolymer at 3400 ypm to form partially oriented round filaments of high denier and nonround filaments of lower denier and of lower elongation, and then draw-texturing at a draw-ratio selected to break no substantial number of filaments prior to passage through a false-twisting device, following which the tension is increased in or after the false-twisting device (using a device, as disclosed in Yu U.S. Pat. No. 3,973,383, for this purpose) so as to break substantially only the lower denier nonround filaments.
Thus, texturing processes, such as draw-texturing and air-jet texturing, exist to develop bulky yarns, and melt-spinning processes have been suggested to prepare mixed yarns whose component filaments will respond differently to the texturing conditions. The resulting textured yarns, however, only approach the spun-like feel of natural fibers, and it would be desirable to improve this quality.
The invention provides an improved process, whereby a mixed yarn of more significantly differing properties can be obtained through a single spinneret, using only a single polymer, if desired, or two polymers, if differential coloring is desired, by effectively providing different extrusion temperatures out of the same spinneret.